There is a couple of open source unreal 4 projects, though:
https://github.com/runeabrahams1/Unreal-Engine-4-Bicycle-Simulator-with-AI
https://github.com/jgcoded/VehicleAIProject
https://github.com/tomlooman/EpicSurvivalGameSeries
https://github.com/Uniname/SplineVehiclePath
Tom Looman’s survival game is the closest to the game you can find, I think.